Magnesium Alloy AZ31B
ASTM AZ31B · UNS M11311 · EN 3.5312 · JIS MB1 · ISO ISO-WD21150
AZ31B is the most widely used wrought Mg-Al-Zn alloy (nominally 3% Al, 1% Zn) and is stocked as sheet, plate and extrusions in O, H24, H22, H26 and F tempers (UNS M11311, 3.5312).
Values for the O condition
AZ31B tempers and conditions
AZ31B is supplied in 5 conditions, soft to hard. O is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ODefault Annealed | Pick for maximum formability and deep drawing (usually warm-formed at 230–290 °C); lowest strength temper. | 150 | 255 | 21 | 49 HB | 18.5 % IACS |
Strain hardened and partially annealed, quarter hard | Lightly cold-rolled then partially annealed AZ31B sheet — strength between O and H24 with useful residual formability. | 190 | 270 | 17 | 65 HB | 18.5 % IACS |
As fabricated | Standard condition for extrusions and forgings per ASTM B107/B91 — no post-extrusion treatment; properties are directional (longitudinal quoted). | 200 | 260 | 15 | 49 HB | 18.5 % IACS |
Strain hardened and partially annealed, half hard | The standard stocked sheet/plate temper: best balance of strength, flatness and usable ductility for machined plate and structural panels. | 220 | 290 | 15 | 73 HB | 18.5 % IACS |
Strain hardened and partially annealed, three-quarter hard | Choose for thin sheet needing the highest as-rolled strength and stiffness with little forming. | 235 | 300 | 10 | 77 HB | 19 % IACS |
What is AZ31B?
AZ31B is the most widely used wrought Mg-Al-Zn alloy (nominally 3% Al, 1% Zn) and is stocked as sheet, plate and extrusions in O, H24, H22, H26 and F tempers (UNS M11311, 3.5312). Engineers select it for a density of 1.77 g/cm³ with 150 MPa yield, 255 MPa tensile strength, 21% elongation and 96 W/m·K thermal conductivity, which suits thin-wall electronics housings and light structural sheet parts. Limits are a 120 °C maximum service temperature, low bare corrosion resistance, and poor cold formability that forces warm bending. AZ61A is the next step when higher strength is required. AZ31B has a density of 1.77 g/cm³ (0.0639 lb/in³), lighter than 86% of magnesium alloy grades. It melts at 566°C (1,051 °F). AZ31B has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 255 MPa (37 ksi) — stronger than 59% of magnesium alloy grades. Elongation at break is 21% and the elastic modulus is 45 GPa (6.53 Msi).
What is AZ31B used for?
- Laptop and tablet housings
- Mobile phone shells
- Camera and optics bodies
- Drone and gimbal frame parts
- Lightweight electronics enclosures and covers
- Extruded structural profiles and rails
- Textile and printing machinery moving parts
Advantages
- Ductile — tolerates forming and impact — 21%, better than 100% of magnesium alloy grades
- Forms and bends easily — 50/100, better than 97% of magnesium alloy grades
Limitations
- Limited service temperature — 120°C (248 °F), worse than 78% of magnesium alloy grades
AZ31B properties
Typical room-temperature values for AZ31B-O; bars are the position among magnesium alloy grades.
Physical3
AZ31B has a density of 1.77 g/cm³ (0.0639 lb/in³), lighter than 86% of magnesium alloy grades. It melts at 566°C (1,051 °F).
Mechanical15
AZ31B has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 255 MPa (37 ksi) — stronger than 59% of magnesium alloy grades. Elongation at break is 21% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AZ31B is rated for continuous service to 120°C (248 °F). It conducts heat at 96 W/m·K (55.5 BTU/hr·ft·°F), better than 50% of magnesium alloy grades. Thermal expansion is 26 µm/m·K (14.4 µin/in·°F).
Electrical3
AZ31B conducts electricity at 18.5 % IACS, worse than 51% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 64% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AZ31B takes about 330 MJ of energy and emits 32 kg of CO₂ — less than 56% of magnesium alloy grades. Typical recycled content is 25%.
Manufacturability8
AZ31B's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability very good (70/100); formability fair (50/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the magnesium alloy family
Yield strength against density for every magnesium alloy grade FabDigit runs. AZ31B is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AZ31B
Is AZ31B easy to machine?
Best machinability of any structural metal — high speeds, sharp positive-rake tools, dry or with mineral oil (never water-based coolant); collect and never let fine chips accumulate, keep Class D extinguishing media on hand.
Can AZ31B be welded?
Readily GTAW/GMAW welded with AZ61A or AZ92A filler and argon shielding; low heat input, no preheat needed on thin sheet, stress-relieve 150 °C/1 h after welding H tempers to avoid SCC.
Can AZ31B be formed, bent or molded?
Cold formability is limited by basal-slip texture — bend/draw warm at 230–300 °C where elongation exceeds 50 %; use generous bend radii (5–7 t cold) and heated tooling.
Manufacturability
The process limits FabDigit's quote engine applies to AZ31B. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Excellent95 / 100 |
|---|---|
| ISO material group | N.7 |
| Cutting speed (rough / finish) | 400 / 460 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 8× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair50 / 100 |
|---|---|
| Weldability | Better70 / 100 |
| Bendable | Yes |
AZ31B chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Alsolid-solution strengthener | 2.5 – 3.5 | 3 |
| Zn | 0.6 – 1.4 | 1 |
| Mnmin 0.20 % for corrosion control (Fe tie-up) | 0.2 – 0.5 | 0.3 |
| Si | ≤ 0.1 | |
| Cu | ≤ 0.05 | |
| Ca | ≤ 0.04 | |
| Fehigh-purity limit | ≤ 0.01 | |
| Nihigh-purity limit | ≤ 0.01 | |
| Others (each)others total 0.30 max | ≤ 0.05 | |
| Mgbalance, ~96 % | balance |
What surface finishes work on AZ31B?
Do not use conventional sulfuric anodize; specify chromate-free conversion coating or Dow 17 / HAE / PEO anodic film plus epoxy primer and topcoat, and isolate from steel/aluminium fasteners to prevent galvanic attack.
Surface treatments FabDigit runs on magnesium alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Conversion Coating
Organic Coating
Equivalent designations
Standards and trade names that resolve to Magnesium Alloy AZ31B in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does AZ31B cost?
AZ31B is a standard-cost magnesium alloy ($$), cheaper than about 59% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
AZ31B — frequently asked
What is AZ31B used for?
AZ31B is typically used for laptop and tablet housings, mobile phone shells, camera and optics bodies, drone and gimbal frame parts, lightweight electronics enclosures and covers and extruded structural profiles and rails. In short: standard wrought magnesium.
What is the yield strength of AZ31B?
AZ31B has a typical yield strength of 150 MPa (21.8 ksi) and a tensile strength of 255 MPa (37 ksi) — stronger than 59% of magnesium alloy grades. Strength varies by condition: see the 5 listed tempers.
Is AZ31B easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Best machinability of any structural metal — high speeds, sharp positive-rake tools, dry or with mineral oil (never water-based coolant); collect and never let fine chips accumulate, keep Class D extinguishing media on hand.
Can AZ31B be welded?
Yes — weldability is rated very good (70/100). Readily GTAW/GMAW welded with AZ61A or AZ92A filler and argon shielding; low heat input, no preheat needed on thin sheet, stress-relieve 150 °C/1 h after welding H tempers to avoid SCC.
What surface finishes work on AZ31B?
Do not use conventional sulfuric anodize; specify chromate-free conversion coating or Dow 17 / HAE / PEO anodic film plus epoxy primer and topcoat, and isolate from steel/aluminium fasteners to prevent galvanic attack.
Can AZ31B be formed, bent or molded?
Cold formability is limited by basal-slip texture — bend/draw warm at 230–300 °C where elongation exceeds 50 %; use generous bend radii (5–7 t cold) and heated tooling.
What is the maximum service temperature of AZ31B?
AZ31B is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AZ31B-O and AZ31B-H26?
O is the default condition — pick for maximum formability and deep drawing (usually warm-formed at 230–290 °C); lowest strength temper. H26: choose for thin sheet needing the highest as-rolled strength and stiffness with little forming. Yield strength is 150 MPa in O versus 235 MPa in H26.
How much does AZ31B cost?
AZ31B is a standard-cost magnesium alloy ($$), cheaper than about 59% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in AZ31B?
Yes — AZ31B is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM B90/B90M — Magnesium-Alloy Sheet and Plate — ASTM International (2021)
- ASTM B107/B107M — Magnesium-Alloy Extruded Bars, Rods, Profiles, Tubes and Wire — ASTM International (2021)
- ASTM B91 — Magnesium-Alloy Forgings — ASTM International (2017)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.